沉水植物附着细菌群落结构及其多样性研究进展

与陆生植物类似,沉水植物的叶表也存在着大量的附着细菌。附着细菌拥有独特的生态位和显著的生态功能,与沉水植物构成了复杂的共生体系。针对附着细菌的群落结构及其多样性进行了简单的综述。在方法学上,"表面活性剂+超声处理"的方式能够比较有效地洗脱叶表的附着细菌。显微计数和分离培养的方法分别发现,某些沉水植物附着细菌的多度在105~107个/cm2以及106 CFU/cm左右。克隆测序的研究表明沉水植物附着细菌的OTU在几十到上百的范围内。在群落结构上,Betaproteobacteria、Bacteroidetes、Alphaproteobacteria、Actinobacteria、Planctomycetes、Cyanobacteria等门类的细菌较为常见。先锋物种在附着细菌生物膜的形成过程中发挥着关键作用,环境条件和植物体都会对附着细菌的多样性造成影响。富营养化水体观察到较高的附着细菌丰度,溶解性有机物比无机营养物更加适合附着细菌的利用。植物体的叶片化学组成、渗出物以及物理结构等会影响附着细菌的多样性及群落结构。对沉水植物附着细菌群落结构形成的机理进行了假说性质的总结,并对附着细菌的研究前沿进行了展望。     

Epibacterial community patterns on marine macroalgae are host-specific but temporally variable

Marine macroalgae are constantly exposed to epibacterial colonizers. The epiphytic bacterial patterns and their temporal and spatial variability on host algae are poorly understood. To investigate the interaction between marine macroalgae and epiphytic bacteria, this study tested if the composition of epibacterial communities on different macroalgae was specific and persisted under varying biotic and abiotic environmental conditions over a 2-year observation time frame. Epibacterial communities on the co-occurring macroalgae Fucus vesiculosus, Gracilaria vermiculophylla and Ulva intestinalis were repeatedly sampled in summer and winter of 2007 and 2008. The epibacterial community composition was analysed by denaturing gradient gel electrophoresis (DGGE) and 16S rRNA gene libraries. Epibacterial community profiles did not only differ significantly at each sampling interval among algal species, but also showed consistent seasonal differences on each algal species at a bacterial phylum level. These compositional patterns re-occurred at the same season of two consecutive years. Within replicates of the same algal species, the composition of bacterial phyla was subject to shifts at the bacterial species level, both within the same season but at different years and between different seasons. However, 7-16% of sequences were identified as species specific to the host alga. These findings demonstrate that marine macroalgae harbour species-specific and temporally adapted epiphytic bacterial biofilms on their surfaces. Since several algal host-specific bacteria were highly similar to other bacteria known to either avoid subsequent colonization by eukaryotic larvae or to exhibit potent antibacterial activities, algal host-specific bacterial associations are expected to play an important role for marine macroalgae.     

盐生植物碱蓬二型果实表生细菌的群落组成及促生属性

【背景】碱蓬(Suaeda glauca Bunge)主要生长于含盐碱土壤,具有果实(种子)二型现象,而种子栖居有众多微生物,它们对种子萌发和幼苗建成具有重要影响。【目的】对碱蓬异型果实表生细菌的群落组成及相关细菌的促生属性进行观察研究,探讨不同类型果实表生细菌的群落组成及相关细菌的促生功能属性是否存在差异。【方法】利用纯培养方法对碱蓬二型果实的表生可培养细菌进行分离纯化,基于16S rRNA基因序列分析初步确定分离菌株的系统发育地位,并对获得菌株进行固氮、溶磷、解钾、产铁及产IAA能力的定性检测。【结果】碱蓬二型果实具有不同的表生细菌群落组成及分布比例,A型果实表生细菌分属于3纲15属,其优势属组成主要是短小杆菌属(34.33%)、芽孢杆菌属(13.43%)和泛菌属(10.45%);B型果实表生细菌分属于4纲20属,其优势属组成主要是短小杆菌属(12.77%)、芽孢杆菌属(17.02%)和冰冻小杆菌属(14.89%)。碱蓬二型果实的表生细菌多样性指数也存在差异,A型果实的Shannon多样性指数、Margalef丰富度指数和Shannon均匀度指数显著低于B型果实;而A型果实的Berger-Parker优势度指数显著高于B型果实。碱蓬二型果实表生细菌在固氮、溶磷、解钾、产铁及产IAA能力等促生属性上的菌株分布比例存在不同变化趋势,A型和B型果实均具有较高比例固氮菌株及较低比例溶磷菌株;但在解钾菌株和产IAA菌株分布比例上具有不同变化趋势,A型果实的解钾菌株所占比例显著高于B型果实,而产IAA能力菌株所占比例显著低于B型果实。【结论】盐生植物碱蓬具有明显不同的2种类型果实,其不同类型果实具有不同的表生细菌群落组成及分布比例,且在促生功能菌株的分布上也存在不同变化趋势。     

Periphyton diatoms in a ditch near Tienhoven

Summary In august 1975, together with other field situations, the diatom composition of a ditch near Tienhoven was studied. Special attention was given to the importance of the different macrophyte species for their epiphytic diatoms. On 5 different sampling stations several parts of every macrophyte species were sampled for diatoms. They were prepared on a special way for determining the species and relative abundance. 119 Species and varieties were found. Most taxa occurred at station 5. The lowest number of taxa was found at station 4. The diatom composition shows a slight relation with the kind of substrate. However, the environmental factors of the surrounding water seem to be more important. To get a good idea of the epiphytic diatom composition on a station at least parts of 50% of the macrophyte species have to be sampled. Some ecological characters of the sampling stations are discussed.     

植物内生细菌测定方法的研究进展

伴随全功能体(holobiont)和全基因组(hologenome)概念的出现,植物微生物群落被看作植物全功能体的重要组成部分,其结构和功能逐渐得到研究和解析.内生细菌是植物微生物群落的成员之一,由于其定殖在组织内部而与宿主的接触更为紧密,因而其与植物的相互作用也更加直接、高效且不容易受到环境条件变化的影响.本文介绍了...     

Physiological state of epiphytic bacteria on submerged stems of the reed Phragmites australis compared with planktonic bacteria in gravel-pit ponds

Suspensions of epiphytic bacteria from submerged stems of Phragmites australis , collected from a gravel-pit pond, were prepared by treatment in a stomacher and by brushing. The two procedures were equally successful in dislodging bacteria. These epiphytic bacteria were compared with planktonic bacteria in water samples from within the reed bed. Colony-forming units (cfu) as a percentage of acridine-orange direct counts (AODCs), percentage of cells capable of intracellular reduction of 2-( p -iodophenyl)-3-( p -nitrophenyl)-5-phenyl tetrazolium chloride (INT) to INT-formazan, percentage of cells able to form microcolonies, and cell length were all greater for epiphytic bacteria. Epiphytic bacteria of P. australis from six further gravel-pit ponds were also compared with bacterioplankton; cfu as a percentage of AODCs, and percentage of cells capable of INT reduction were again greater for epiphytic bacteria. Because the epiphytic bacteria in these non-organically-enriched, gravel-pit ponds were physiologically different from the planktonic bacteria it is suggested that there was not continual casual exchange, by largely identical bacterial cells, between the epiphytic and planktonic mode. Instead, epiphytic and planktonic populations were independent of each other and/or if there was exchange then bacteria were more successful while in the attached mode, perhaps because of greater organic-nutrient availability at the stem surface.     

An assessment of some improved techniques for estimating the abundance (frequency) of sedentary organisms

The traditional sampling method for estimating frequency (the number of sub-quadrats containing a basal part of the organisms) is compared, using both computer simulations and direct comparison in the field, to two new methods that use a compound series of variable-sized concentric sub-quadrats. Both the new frequency-score and the new importance-score methods are closer approximations of density than is the standard frequency method, and the estimates produced by both of the new methods are less affected by the choice of sub-quadrat size and the spatial distribution (dispersion) of the organisms (i.e. clumping and regularity). Thus, the two nested-quadrat methods appear to ameliorate the usual frequency limitations associated with sub-quadrat size and organism dispersion, by the use of a range of different sub-quadrat sizes. This is important in community studies, where the component species may show a wide range of densities and dispersions. Both of the new methods are easily employed in the field. The importance-score method involves no more sampling effort than does standard qualitative (presence-absence) sampling, and it can therefore be used to sample a larger quadrat area than would normally be used for frequency sampling. This makes the method much more cost-effective as a means of estimating abundance, and it allows a greater number of the rarer species to be included in the sampling. The frequency-score method is more time-consuming, but it is capable of detecting more subtle community patterns. This means that it is particularly useful for the study of species-poor communities or where small variations in composition need to be detected.     

山西省辛安泉泉域三种泉溪大型藻类植物附生藻类的研究

对三种泉溪大型藻类(脆弱刚毛藻, 弧形串珠藻和普生轮藻)藻体上附生藻类的种类、分布及环境因子与寄主本身对其的影响进行了研究。2004 年7 月至2005 年4 月在山西省辛安泉泉域采集三种大型藻类植物(每个季节采集一次)。研究结果表明, 三种大型藻类藻体上的附生藻类种类数不同, 普生轮藻上的附生藻类有49 种, 脆弱刚毛藻上37 种, 弧形串珠藻上6 种, 其中硅藻门种类数最多。这说明寄主本身结构的复杂程度在一定意义上会影响附生藻类的种类数及多样性。就季节变化而言, 三种大型藻类藻体上的附生藻类也表现出了明显的季节性,大致趋势为: 春季>秋季>夏季>冬季, 同时, 灰关联分析结果也表明, 环境因子在一定程度上对附生藻类也有影响, 最关键的影响因子是流速、水深和电导。这说明影响大型藻类植物藻体上附生藻类的影响因素是多方面的, 不仅有寄主本身, 同时流速、水深和电导这三种环境因子也起到了很关键的作用。       

Comparison of the Phenotypes and Genotypes of Biofilm and Solitary Epiphytic Bacterial Populations on Broad-Leaved Endive

The discovery that biofilms are ubiquitous among the epiphytic microflora of leaves has prompted research about the impact of biofilms on the ecology of epiphytic microorganisms and on the efficiency of strategies to manage these populations for disease control and to ensure food safety. Biofilms are likely to influence the microenvironment and phenotype of the microorganisms they harbor. However, it is also important to determine whether there are differences in the types of bacteria within biofilms compared to those outside of biofilms so as to better target microorganisms via disease control strategies. Broad-leaved endive (Cichorium endivia var. latifolia) harbors biofilms containing fluorescent pseudomonads. These bacteria can cause considerable post-harvest losses when this plant is used for manufacturing minimally processed salads. To determine whether the population structure of the fluorescent pseudomonads in biofilms is different from that outside of biofilms on the same leaves, bacteria were isolated quantitatively from the biofilm and solitary components of the epiphytic population on leaves of field-grown broad-leaved endive. Population structure was determined in terms of taxonomic identities of the bacteria isolated, in terms of genotypic profiles, and in terms of phenotypic traits related to surface colonization and biofilm formation. The results illustrate that there are no systematic differences in the composition and structure of biofilm and solitary populations of fluorescent pseudomonads, in terms of either genotypic profiles or phenotypic profiles of the strains. However, Gram-positive bacteria tended to occur more frequently within biofilms than outside of biofilms. We suggest that leaf colonization by fluorescent pseudomonads involves a flux of cells between biofilm and solitary states. This would allow bacteria to exploit the advantages of these two types of existence; biofilms would favor resistance to stressful conditions, whereas solitary cells could foster spread of bacteria to newly colonizable sites on leaves as environmental conditions fluctuate.     

Assessing the effects of forest management on epiphytic lichens in coppiced forests using different indicators

Abstract

Epiphytic lichens are one of the taxonomic groups most sensitive to forest management. Nevertheless, they have not yet been exhaustively included in the assessment of Sustainable Forest Management. This work aimed at evaluating the effects of forest management on epiphytic lichens in coppiced forests, exploring the spatial patterns of diversity and the composition of communities. Moreover, the goal was to compare the performance of four potential indicators for monitoring the effects of forest management on epiphytic lichens: total lichen diversity, species associated with intensive management, species associated with aged coppiced woodlands and Indicator Species Ratio (ISR). In humid Mediterranean Liguria, 50 sampling units were chosen in Castanea sativa and deciduous Quercus spp. forests subjected to different forest management practices: intensively managed coppice and aged coppice/high forest. The effect of forest management was evident in terms of species composition, since it was possible to find significantly associated species for each of the two management types. At each sampling site, the four indicators were calculated using Indicator Value Analysis and compared through correspondence analysis. The ISR was shown to be a more effective indicator, being independent of floristic composition and the occurrence of rare species.     

Population Sizes, Immigration, and Growth of Epiphytic Bacteria on Leaves of Different Ages and Positions of Field-Grown Endive (Cichorium endivia var. latifolia)

Total, fluorescent, and pectolytic epiphytic bacterial population sizes were quantified on leaves of different age groups of broad-leaved endive during field cultivation from leaf emergence until harvest. Greater bacterial population densities (log(inf10) CFU per square centimeter) were observed on outer leaves than on inner leaves of the plants throughout the growing season. These differences were statistically significant for total bacterial populations at all sampling times and were often significant for fluorescent and pectolytic bacterial populations. At harvest, a linear gradient of decreasing densities of epiphytic bacteria from outer (older) to inner (younger) leaves of the head was significant. Leaf age influenced the frequency distribution and variability of bacterial population sizes associated with leaves of broad-leaved endive. Total bacterial population sizes were greater at leaf emergence for leaves emerging during the second half of the cultivation period than for leaves emerging earlier. The size of fluorescent and pectolytic bacterial populations on newly emerged leaves increased throughout the season as plants aged. To assess the importance of plant age on bacterial immigration at leaf emergence, bacterial densities were quantified on leaves emerging simultaneously on plants of different ages. In two of the three experiments, greater bacterial population sizes were observed on leaves emerging on younger plants. This indicates that factors other than an increase in concentration of airborne bacteria can lead to increases in population sizes at leaf emergence as plants age in the field. Results of leaf pruning experiments suggested that adjacent leaves may act as a barrier for immigration of fluorescent bacteria on newly emerged leaves. Survival of an inoculated strain of Pseudomonas fluorescens on newly emerged leaves generally did not vary with the age of plants. However, these effects were not consistent among experiments, suggesting that interactions among micro- and macroenvironmental conditions, physiological condition of leaves, and accessibility of leaves to airborne bacteria are important in controlling epiphytic bacterial population sizes.     

Field Evaluation of Personal Sampling Methods for Multiple Bioaerosols

Ambient bioaerosols are ubiquitous in the daily environment and can affect health in various ways. However, few studies have been conducted to comprehensively evaluate personal bioaerosol exposure in occupational and indoor environments because of the complex composition of bioaerosols and the lack of standardized sampling/analysis methods. We conducted a study to determine the most efficient collection/analysis method for the personal exposure assessment of multiple bioaerosols. The sampling efficiencies of three filters and four samplers were compared. According to our results, polycarbonate (PC) filters had the highest relative efficiency, particularly for bacteria. Side-by-side sampling was conducted to evaluate the three filter samplers (with PC filters) and the NIOSH Personal Bioaerosol Cyclone Sampler. According to the results, the Button Aerosol Sampler and the IOM Inhalable Dust Sampler had the highest relative efficiencies for fungi and bacteria, followed by the NIOSH sampler. Personal sampling was performed in a pig farm to assess occupational bioaerosol exposure and to evaluate the sampling/analysis methods. The Button and IOM samplers yielded a similar performance for personal bioaerosol sampling at the pig farm. However, the Button sampler is more likely to be clogged at high airborne dust concentrations because of its higher flow rate (4 L/min). Therefore, the IOM sampler is a more appropriate choice for performing personal sampling in environments with high dust levels. In summary, the Button and IOM samplers with PC filters are efficient sampling/analysis methods for the personal exposure assessment of multiple bioaerosols.     

Summer season and long-term drought increase the richness of bacteria and fungi in the foliar phyllosphere of Quercus ilex in a mixed Mediterranean forest

We explored the changes in richness, diversity and evenness of epiphytic (on the leaf surface) and endophytic (within leaf tissues) bacteria and fungi in the foliar phyllosphere of Quercus ilex, the dominant tree species of Mediterranean forests. Bacteria and fungi were assessed during ontogenic development of the leaves, from the wet spring to the dry summer season in control plots and in plots subjected to drought conditions mimicking those projected for future decades. Our aim was to monitor succession in microbiota during the colonisation of plant leaves and its response to climate change. Ontogeny and seasonality exerted a strong influence on richness and diversity of the microbial phyllosphere community, which decreased in summer in the whole leaf and increased in summer in the epiphytic phyllosphere. Drought precluded the decrease in whole leaf phyllosphere diversity and increased the rise in the epiphytic phyllosphere. Both whole leaf bacterial and fungal richness decreased with the decrease in physiological activity and productivity of the summer season in control trees. As expected, the richness of epiphytic bacteria and fungi increased in summer after increasing time of colonisation. Under summer dry conditions, there was a positive relationship between TRF (terminal restriction fragments) richness and drought, both for whole leaf and epiphytic phyllosphere, and especially for fungal communities. These results demonstrate that changes in climate are likely to significantly alter microbial abundance and composition of the phyllosphere. Given the diverse functions and large number of phyllospheric microbes, the potential functional implications of such community shifts warrant exploration.     

A quantitative study of the epiphytic vegetation on pollarded trunks of Fraxinus excelsior at Havrå, Osterøy,western Norway

The epiphytic vegetation on 19 pollarded trees of Fraxinus excelsior at the farm Havrå, Osterøy, western Norway was investigated. Each trunk was divided into a basal zone, a middle zone and a top zone. In each zone the four different aspects were analysed by squares (12 sampling units from each trunk). Within a total of 225 sampling units, 173 taxa were recorded (84 lichens, 72 bryophytes, 17 vascular plants). The epiphytic vegetation was classified into seven TWINSPAN groups, and it is shown by detrended correspondence analysis (DCA) that these groups are mainly separated by the first two DCA axes. In an attempt to explain the floristic composition, several environmental variables were measured, and the floristic and environmental data were analysed by canonical correspondence analysis (CCA). A pollarded tree, depending on its age, represents a continuum of perhaps several hundred years. Some of the recorded epiphytic lichens are very rare in Norway, and the pollarded trees thus contribute greatly to the biodiversity of the old cultural landscape. Several epiphytic species take advantage of favourable light conditions on trunks in the open fields. At Havrå, woodland has developed by tree colonization of old meadows and open fields during the last 40 years after the cessation of earlier managements. Some floristic differences between the epiphytic vegetation on trunks in the open fields and in the woodland are found. This suggests a change in the epiphytic vegetation because of the creation of a more shady habitat in parts of the area during a few decades.     

Quantitative observations on the ability of epiphytic bacteria to contribute to the populations of suspended bacteria in two dissimilar headstreams

SUMMARY. 1. Concentration of suspended bacteria in a calcareous headstream increased linearly from the source to 48 m; this indicated a diffuse origin of bacteria.
2. Drift loss of suspended bacteria and glucose-mineralization capacity from this length of stream were measured, and estimates were also made of the total number and glucose-mineralization capacity of epiphytic bacteria associated with the luxuriant submerged aquatic vegetation.
3. Mean drift loss per day represented 11–12% of total epiphytic bacteria and 8–18% of epiphyte glucose-mineralization capacity, hence the epiphytic population should be well able to sustain the observed downstream losses.
4. In a 90 m length of a contrasting acid, granitic, headstream, in which submerged vegetation was principally a leafy liverwort, there was no downstream change in concentration of suspended bacteria.
5. A substantial population of epiphytic bacteria was found in the acid stream, sufficient for only a 1–2% daily release to produce a doubling in concentration of suspended bacteria; reasons are suggested for the apparent non-release of epiphytes.     

Growth form analysis of epiphytic diatom communities of Terra Nova Bay (Ross Sea, Antarctica)

Diatoms have been long collected from the Southern Ocean but almost no data exist for epiphytic communities, despite their high ecological significance as an important food source in Antarctic coastal food chains. Here, we present a first growth form analysis of diatoms associated with rhodophyte hosts from Terra Nova Bay, Ross Sea, Antarctica. We performed this study to gather baseline information on the species composition of epiphytic diatom communities, determine the influence of some environmental variables on the diatom distribution patterns, and assess the caveats that must be taken into account in terms of sampling design. Macroalgal material was collected during the Italian Antarctic expeditions between 1990 and 2004. Epiphytic diatoms were studied by means of scanning electron microscopy. In terms of growth forms, there were no significant differences between the diatom communities on the different macroalgal host species. Motile (mainly small-celled Navicula perminuta and other Navicula spp.) and adnate (Cocconeis spp.) diatoms dominated the community throughout the study period. Many of the macroalgal blades examined were also covered by epiphytic animals (calcareous bryozoans, hydroids) over most of their surface, with a significant effect on the associated diatom community structure. Our findings suggest that the bio-physicochemical characteristics of each sampling site affected the epiphytic diatom communities more than the substrate type provided by the macroalgal host or the sampling depth.     

Influence of nitrate—ammonium ratio on growth and nutrition of Arabidopsis thaliana

We investigated the microbial community structure and population size of arboreal soils—including canopy and bromeliad epiphytic leaf-tank soils—and ground soils in a tropical lowland rainforest in Costa Rica using molecular and cultivation methods. PCR-DGGE analysis of 16S rRNA and 18S rRNA gene fragments and quantitative real-time PCR were applied to survey the bacteria, ammonia-oxidizing bacteria (AOB), and fungi. Bacteria from epiphytic tank soils were isolated and identified. Bacillaceae, Pseudomonadaceae and Micrococcaceae were the most abundant families. According to cluster analysis of DGGE fingerprints a significant difference among the three soil types was evident for bacterial communities. In addition, the microbial communities of canopy and tank soils clustered apart from ground soils. The fungal and AOB communities were diverse but non-specific for the soil types analyzed.     

Epiphyton as a niche for ammonia-oxidizing bacteria: detailed comparison with benthic and pelagic compartments in shallow freshwater lakes

Next to the benthic and pelagic compartments, the epiphyton of submerged macrophytes may offer an additional niche for ammonia-oxidizing bacteria in shallow freshwater lakes. In this study, we explored the potential activities and community compositions of ammonia-oxidizing bacteria of the epiphytic, benthic, and pelagic compartments of seven shallow freshwater lakes which differed in their trophic status, distribution of submerged macrophytes, and restoration history. PCR-denaturing gradient gel electrophoresis analyses demonstrated that the epiphytic compartment was inhabited by species belonging to cluster 3 of the Nitrosospira lineage and to the Nitrosomonas oligotropha lineage. Both the ammonia-oxidizing bacterial community compositions and the potential activities differed significantly between compartments. Interestingly, both the ammonia-oxidizing bacterial community composition and potential activity were influenced by the restoration status of the different lakes investigated.     

Comparison of Diversity and Functions of Epiphytic Bacteria from Cultivated and Weed Plants in Agrocenoses

Diversity of epiphytic bacterial complexes from cultivated and weed plants was compared according to the frequency of predominance of bacterial taxa in these communities and using the principal component method. The presence of both common dominants on cultivated and weed plants and distinct differences in the composition of the epiphytic bacterial complexes of these plants was revealed. The representatives of chemolithotrophic bacteria capable of tetrathionate and thiosulfate assimilation were found only on weed plants. The antibiotic activity of bacteria isolated from weed plants was almost twice as high as that found for bacteria from cultivated plants. The obtained data indicate the positive effect of bacterial communities of weed plants, which make it possible to protect cultivated plants from phytopathogens.     

海南岛不同林龄木麻黄凋落物内外细菌多样性及其化感潜力

凋落物在生态系统中具有重要作用。为了对比凋落物内外微生物的多样性和群落结构,选取海南省海口市桂林洋海滨区3个林龄木麻黄凋落物为研究对象,采用Illumina Miseq高通量测序,对凋落物内外微生物的多样性和组成进行分析。结果表明: 凋落物外生细菌的多样性高于内生细菌,中龄林凋落物内外细菌多样性和丰富度均最高,其次是幼龄林,成熟林最低。菌群群落组成分析表明: 在门分类水平上,变形菌门和放线菌门最为丰富(约占总数的80%);属水平上,短小杆菌属、Jatrophihabitans、分支杆菌属、放线孢菌属、Mucilaginibacter、假单孢菌属等在不同林龄间表现出显著差异。主坐标分析(PCoA)表明,凋落物内生细菌受林龄的影响较大,而外生细菌受环境因子的影响较大;解淀粉芽孢杆菌发酵液对木麻黄种子化感潜力最强,且其中含有2,2′-亚甲基双-(4-甲基-6-叔丁基苯酚)等化感物质,表明解淀粉芽孢杆菌参与了化感物质的合成。凋落物微生物群落多样性对木麻黄的化感作用有一定影响,这为探讨微生物在木麻黄凋落物降解过程中作用的研究奠定基础。